In the coming year, emphasis of our program will be in the area of iron metabolism. Areas of study include the molecular mechanism of iron absorption, regulation of iron exchange between transferrin and tissues, pathway of iron movements through cells and its regulation, tissue abnormalities with iron deficiency anemia, an attempt to develop an experimental animal with parenchyml iron overload. In addition, studies will be commenced on the in vitro maintenance of red cells at 37 degrees, on the quantitative evaluation of marrow function, and on granulocyte kinetics in the experimental animal and in man.